Matrix for regenerative heat exchangers



United States Patent `O 3,183,963 MATRIX FOR REGENERATIVE HEAT EXCHANGERS James R. Mondt, Warren, Micl., assgnor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Jan. 31, 1963, Ser. No. %5,336 4 Claims. (Cl. 165-10) This invention relates to heat exchangers and more particularly to a matrix of superposed sheets suitable for transferring heat received from one fluid to another.

Attention is directed to regenerative heat exchangers as described in the United States Patents No. 2,893,699, granted July 7, 1959, in the name of W. C. Bubniak and No. 2,937,010, granted May 17, 1960, in the names of J. S. Collman and W. A. Turunen. Such exchangers are used for transferring heat from hot combustion turbine exhaust gas to cold turbine intake gas by means of a matrix which alternately stores and gives up heat as it is alternately contacted by hot and cold gas. Such a matrix may comprise laminae or cylindrical sheets between which the hot and cold gases are alternately passed in paths extending in a given general direction with respect to and toward and then through the matrix.

An object of the present invention is to provide an improved matrix exhibitingoptimum heat exchange characteristics for use in a regenerative heat exchanger.

A feature of the invention is a matrix of superposed corrugated sheets each having a specific geometrical form with relation to the general path of flow of a fluid about to enter the spaces defined between the sheets whereby the storing and giving up of thermal energy may be eifected with high efficiency.

These and other important features of the application will now be described in detail in the specification and then pointed out more particularly in the appended claims.

In the drawings:

FIGURE 1 is a plan view of portions of a few sheets comprising a matrix of the present invention as related with a duct determining the general direction of flow of a fluid about to enter the matrix;

FIGURE 2 is a perspective and exploded view of the sheet portions shown in FIGURE 1 but with the form of corrugations more clearly illustrated;

FIGURE 3 is a plan View of a modified sheet suitable for use in the matrix;

FIGURE 4 is a plan view of another modified sheet;

FIGURE 5 is a plan view of a third form of sheet; and

FIGURE 6 is an enlarged cross sectional view of V-shaped corrugations formed in the sheets of FIGURES 1 to 5 inclusive.

It has been found that the geometry of the sheets making up the matrix is crucial if a maximum heat transfer per unit of pressure drop is to be obtained. The materal thickness t (FIGURE 6) of each sheet in a given matrix is not critical but the present invention is particularly applicable to a matrix in which the dimension t of each sheet preferably falls within the range of .0005 of an inch to .01 of an inch.

As the improvement in heat transfer characteristics is dependent upon the geometrical layout of the sheets, the nature of the sheet material may be varied widely. Stanless steel, aluminum, copper, ceramic or even Wood or paper could be used. The essential characteristic of the sheet material in practicing the present invention is that it possess the ability to store heat and all sheet materials are capable of storing heat to some extent. p

In the drawings, the lengths of all corrugations are shown as extending at an angle of approxirnately 10 degrees with the general direction of fluid flow at the en- "ice trance side or upstream of the stack or matrix made up of superposed sheets. This angle is represented at a in FIGURE 1 and it should be understood that a greatly improved result in both storing and giving up heat is realized when the angle a is given a value within the range of 5 to 20 degrees. Reducing this angle below 5 degrees reduces the heat transfer capability and increasing it beyond 20 degrees unduly increases the flow resistance.

VFIGURE l` shows a plurality of corrugated metal sheets 10, 12, 14, 16. They are superposed and the lengths of the V-shaped corrugations of the alternate sheets 10 and 14 extends 10 degrees to the right (FIGURE 1) with the general direction of fluid flow from a diagrammatically represented duct 20. This direction of fluid immediately about to enter between the sheets is represented by arrows b and -is parallel with the planes of the sheets. The lengths of the V-shaped corrugations of the sheets 12 and 16 also extend 10 degrees with the direction b but to the left. The crossng or traversing of the corrugations of adjace'nt plates prevents nesting and determines the required intricate passages for fluid flow through the matrix. As stated above, the angularity a may vary from 5 to 20 degrees in realizing the advantages of the present invention and this means that the lengths of the oorrugations of a given sheet extend at an angle of from 10 to 40 degrees with the lengths of the corrugations of an adjacent sheet.

The hydrodynamic function known as the Reynolds number has a fundamcntal hearing in realizing the advantages of the present invention. It is known that when the Reynolds number is less than 2100 in a long passage of -circular flow cross section the flow 'of fluid will be viscous (straight line flow) as distinguished from turbu lent (mixed). The Reynolds number is `a dimensionless parameter commonly known in the fields of fluid flow and heat transfer as the ratio of flow inert ia forces to viscous forces and is used to establish the condition of dynamic similarity in the flow field. In practicing the present invention, the Reynolds number falls within the viscous range of from 10 to 1000.

Experimentation has also shown that if the pronounced improvement in heat transfer is to be realized the ratio of corrugation pitch p (FIGURE 6) to corrugation height h should fall within the range of 2 to 3 and the ratio of corrugation height h to ;stock or sheet thickness t should be from 5 to 20.

FIGURE 3 shows a sheet 22 having corrugations similar to those in sheets 10 and 14 but in this instance staggered slots 24 are formed in the sheet before the sheet is corrugated. These slots cause the sheet 22 better to lie straight and conform With the desired shape of a matrix of which it is to form a part. The loss of metal because of the forming of the slots may cause a slight loss in heat transference but this is inconsequential. There is a slight increase in fluid friction as compared with solid sheets.

FIGURE 4 depicts a sheet 26 having slits 28 in somewhat staggered relat-ion. The slits avoid stock removal necessary in making slots and therefore no heat transfer ability is lost as Compared with the sheets of FIGURE 1. The term slits as used herein may be taken to include slots." There is no discernible difference between the solid and slitted sheets insofar as fluid friction is concerned.

A part of a sheet 30 is shown in FIGURE 5 and this sheet is corrugated in :a herringbone or chevron design. With such sheets superposed in a stack or matrix with the apices of the corrugations in adjacent sheets oppositely directed, the advantages of heat transference of the present invention are obtained at no cost of increased flow resistance hence one or many apioes may be used. slits 32 are utilized as a distinct aid in mainta ining sheet flatness. All slit and slot patterns also improve heat ex- &183363 Changer performance by reducing longitudinal thermal conduction heat transfer through the solid sheets.

Although matrices made with corrugated sheets as depicted in the drawings are specifically designed for the handling of gases, the principles of the invention also are applicable to liquids. The invention, therefore, may accurately be described in connection with a "fluid. It should also be noted that, although the leading edge 34 or the trailing edge 38 of a sheet 10 (taken as representative) is shown normal to the direction or fluid path b, those edges may be at other angles without an adverse eflect on the heat exchange characteristics. The most important geometrical .aspect is the relation of the corrugation sides to the path or direction b. Another aspect should also be noted and that is that many variations from the V-shape in forming the cross-:section of each corrugation are possible while retaining to a large degree the advani tages of the present invention.

I claim:

1. A matrix for regenerative heat exchangers for aflecting a fluid, said matrix eomprising a stack of at least three superimposed sheets, each of said sheets having corrugations, the corrugations of at least one of said sheets being in contact with and traversing the corrugations of adjacent sheets preventing nesting, means defin-ing a general direction of an entrance path for a fluid parallel ?and aligned with the planes of said sheets, said means and sheets being cooperatively arranged in proximity to introduce and discharge said fluid the length of each of said corrugations extend-ing at an angle within a range of to 20 degrees with the :said fluid entrance path, and slits formed transverse to said corrugations in each of said sheets.

2. A matrix for regenerative heat exchangers comprising a stack of at least three superimposed sheets, spaces in said stack defining a general path for a fluid extending parallel with the planes of said sheets, each of said sheets having a thickness of .0005 to .01 of an inch and having parallel corrugations in contact with and traversing the corrugations of an adjacent sheet, staggered slits in each of said sheets and extending transverse to the said general path, each of said corrugations having a pitch to height ratio of 2 to 3 and extending at an angle within the range of 5 to 20 degrees With the said general fluid path, and the arrangement being such that the Reynolds number regime in heat transfer relation with said fluid is from 10 to 1000.

3. A matrix for a regenerative heat exchanger, said matrix comprising a stack of at least three superimposed sheets, Conduit means adjacent to :said stack and defining a general entranoe path for fluid extending toward said stack and parallel with the planes of said sheets, each of said sheets having a material thickness of .0005 to .01 of an inch and corrugations in herringbone form, the ridges of the corrugations extending at an angle within the range of 5 to 20 degrees with the said general entrance path, and staggered slits in each of said sheets extending across some of said ridges.

4. A matrix for a regenerative heat exchanger, said matrix comprising a stack of at least three superimposed sheets in c-ontactual relation, conduit means adjacent to said stack and defining a general entrance path for fluid extending to said stack and parallel with the planes of said sheets, each of said sheets having a material thickness of .0005 to .01 of an inch and parallel corrugations, the ridges of the corrugations extending'at an angle within the range of 5 to 20 degrees with the said general entrance path, and the ridges in at least one of said sheets extending across and Contacting the 'idges of the adjacent sheets to prevent nesting. i

References Cited by the Examiner UNITED STATES PATENTS 2,023,965 12/35 Lysholm 165-10 X v 2,602,645 7/ 52 Benenati et -al 165--10 X 2,692,131 10/54 Hasche 165-10 X 2,696,976 12/54 Boestad et al. 165-10 2,701,13O 2/55 Boestad l65-10 FOREIGN PATENTS 848,095 9/ Great Britain.

CHARLES SUKALO, Pr'mary Exam'ner.

MEYER PERLIN, Exam'ner. 

1. A MATRIX FOR REGENERATIVE HEAT EXCHANGERS FOR AFFECTING A FLUID, SAID MATRIX COMPRISING A STACK OF AT LEAST THREE SUPERIMPOSED SHEETS, EACH OF SAID SHEETS HAVING CORRUGATIONS, THE CORRUGATIONS OF AT LEAST ONE OF SAID SHEETS BEING IN CONTACT WITH AND TRAVERSING THE CORRUGATIONS OF ADJACENT SHEEETS PREVENTING NESTING, MEANS DEFINING A GENERAL DIRECTION OF AN ENTRANCE PATH FOR A FLUID PARALLEL AND ALIGNED WITH THE PLANES OF SAID SHEETS, SAID MEANS AND SHEETS BEING COOPERATIVELY ARRANGED IN PROXIMITY TO INTRODUCE AND DISCHARGE SAID FLUID THE LENGTH OF EACH OF SAID CORRUGATIONS EXTENDING AT AN ANGLE WITHIN A RANGE OF 5 TO 20 DEGREES WITH THE SAID FLUID ENTRANCE PATH, AND SLITS FORMED TRANSVERSE TO SAID CORRUGATIONS IN EACH OF SAID SHEETS. 